There are a number of vitreous and retinal problems for which intraocular gas injections are indicated. This technique has gained wide acceptance over the past decade and is often performed in conjunction with vitrectomy and scleral buckling operations. Problems amenable to treatment with intraocular gas include volume restoration unfurling a giant retinal tear, sealing a gaping or posterior retinal break, flattening a meridional fold and locating an obscure retinal break. Due to their high molecular weight and low water solubility, the perfluorocarbon gas bubbles expand initially after intraocular injection because the more soluble blood gases are drawn into the eye. While the expansivity of the perfluorocarbon gases can be used advantageously, this factor precludes filling the entire eye with gas at the time of surgery. The purpose of this investigation is to determine the perfluorocarbon blood gas mixtures which are nonexpanding which will last for the longest time. These mixtures can then be used to fill the entire eye without risk of expansion and causing high pressure. The gases to be studied in a rabbit experiment include the perfluorocarbon gases CF4, C2F6, C3F8, C4F10 and SF6. This will be done in the following short-term steps which could be accomplished within one month for each gas tested. (1) Confirming the time for maximum expansion of a pure intraocular perfluorocarbon gas injection by the direct method. (2) Determination of the composition of the maximally expanded bubble. (3) Preparation of the gas as determined in 2. (4) Injection of the prepared gas and determination of its volume change over time.